Battery choices

The best battery is a small one, right? Unfortunately the reality is lot more complex than that and a battery powered system might not last as long without a charge as you think if the battery does not match up well with the system it’s powering.

Keith Odland at Silicon Laboratories has written an overview of battery chemistries and their effect on system design at EDN. He notes how hearing aids often use zinc-air batteries, which have a terrible lifetime of mere months, because they pack a lot of energy into a small space and still provide high peak currents. The designers work around the low, 1.4V output these cells can generate. Other systems might have to trade density for lifetime and use capacitors to deliver high peak currents.

Odland goes on to examine the tradeoffs of using boost and LDO converters or dynamically switching the voltage rails to deliver the best efficiency for a low-power sensor node that has a high-voltage transmitter circuit operating alongside a lower-voltage receiver. In this case, cutting out the LDO works out more efficient.

Posted by Chris Edwards

The Low-Power Design Blog is sponsored by Mentor Graphics. The company has focused years of R&D on low-power design techniques and is glad to support a resource that highlights creative methods for reducing the power consumption of electronic systems.